Watermarking digital data at a user device

ABSTRACT

A method of watermarking digital media data in a user device using a watermark that contains information derived from the digital media data content and the user device specific information to enable improved enforcement of the digital media data content copyright license.

This application claims the benefit of the U.S. Provisional ApplicationNo. 60/404/884 filed on Aug. 21, 2002.

FIELD OF THE INVENTION

The present invention relates to digital media content protection, andmore particularly, to a method of watermarking digital media data forthe purpose of authenticating copyright ownership and copyrightprotection.

BACKGROUND OF THE INVENTION

Multimedia data content protection is a very significant problem facingcontent providers. Current content protection methods rely on encryptionto protect the multimedia data content with the assumption that onlyauthorized users have the key to decrypt the encrypted multimedia datacontent. However, this does not prevent the user from taking theunencrypted and uncompressed signal from the user's device andre-encoding it for illegal distribution.

One method of copyright protection utilized in digital multimediaindustry is watermarking of the digital multimedia signal (e.g. videoand/or audio signals). A watermark is a digital code embedded in the bitstream of the digital multimedia signal which typically indicates theidentity of the copyright owner. When watermarking is applied toindividual copies of digital audio or video data, such as audio CDs orvideo DVDs, watermarking may also be used to indicate the identity ofthe licensed receiver of each copy. Then, illegally reproduced copiescan be traced back to the original receiver.

In a known application for watermarking multimedia data, the watermarksignal is uniquely defined by user device specific information.Typically, this would be the user device's unique machine ID. Forexample, some DVD player manufacturers incorporate watermarking enginesin their DVD players so that a unique watermark is added into theuncompressed video output signal. The watermark contains the uniquemachine ID of the particular DVD player which generates the watermarksignal. If the video from the output of the DVD player is then recorded,the recorded copy would be watermarked with information identifying theparticular DVD player used to make the unauthorized copy.

However, using the machine ID alone to determine the watermark signalhas some limitations. First, it is a static piece of information foreach user device so it does not change. This dictates that the watermarksignal will exhibit a relatively stable characteristic pattern for agiven user device. Such pattern can be detected relatively easily andthe watermark signal may be isolated and removed. Secondly, since theinformation contained in the watermark is limited, for example, to onlythe machine ID, the type of content distribution control based on suchinformation is thus also quite limited.

Thus, improved watermarking methods are desired.

SUMMARY OF THE INVENTION

According to an aspect of the present invention, there is disclosed amethod of watermarking digital media data in a user device, such as a CDplayer, a DVD player, or a video set-top box where the watermarkcontains information derived from the digital media data content inaddition to the user device specific information. Digital media data asused in this application may be multimedia data (i.e. including videoand audio data) or video data alone or audio data alone. In a typicaldigital content distribution framework, media data, when received at theuser device, is generally encrypted for protection. In order to decryptthe content, the user device typically needs to obtain a copyrightlicense from the digital media content provider. The copyright licenseis normally provided separate from the content and includes a key todecrypt the content. The copyright license may also contain informationthat is used to control the playback of the content. For example, thelicense may specify which machine the license is limited to and theexpiration date of the license. After decrypting the digital media data,the user device will decode to uncompress the digital media data. Then,the user device will use both the information contained in the licensedata and the user device's unique identification information to generatea watermark. The watermark is then embedded into the decrypted anduncompressed digital media content. There are a number of signalprocessing methods, well known in the art, for the generation of awatermark and embedding of a watermark into a host signal. Any suchmethods may be employed in this invention.

Watermarking digital media data using a watermark that includesinformation derived from the digital media data content and an userdevice specific information provides a number of benefits to thecopyright protection scheme in digital content distribution framework.Firstly, it provides the digital media data content providers anopportunity to be more involved in the content protection process. Sincecontent providers are often the parties most concerned about contentprotection, enhancing their ability to better control the process isdesirable. Secondly, the watermark that is embedded in the output signalof the user device will contain more comprehensive information than thatfound in the conventional watermarking scheme. For example, thewatermark generated according to an embodiment of the present inventioncontains user device specific information, such as the device's uniquemachine ID, and information derived from the copyright licenseassociated with the digital media data content. The copyright licenserelated information would include subscriber/buyer information, anyrules that regulate the use of the digital media data content, such as,for example, the specific device for which the digital media datacontent is intended, the expiration date of the copyright license,whether the digital media data content can be redistributed(distribution rights), what geographical locations can view the digitalmedia data content (geographical limitations), as well as the contentprovider information. Such comprehensive content-related information canbe used to determine the origin of the digital media data content, thetargeted devices of the digital media data content and the lifetime ofthe digital media data content, which may be used for more effectivecopyright protection of the digital media data content.

The watermarking method according to an aspect of the present inventioncan be used by the digital media data content providers to moreeffectively detect copyright infringement and trace the origin of theinfringement. Since comprehensive content-related information (includingcontent provider information and content distribution rights) isembedded in the content as part of the watermark together with the userdevice ID, content providers can easily track their contents bysearching for the watermark pattern related to their unique information.Once such contents are located, the digital media data content providerscan then determine whether the contents are distributed as specified bythe original distribution rights. If a piece of digital media content isan illegal copy, the culprit device, as well as the identity of thecontent from which the illegal distribution originated, can beidentified using the content-related information in the watermarksignal.

BRIEF DESCRIPTION OF THE DRAWING

The invention will be better understood from the following detaileddescription of an exemplary embodiment thereof in conjunction with theaccompanying drawing in which:

FIG. 1 is a schematic representation of a user device capable ofperforming a method of watermarking digital media data according to anembodiment of the present invention.

DETAILED DESCRIPTION

Referring to FIG. 1, a user device 100 according to an embodiment of thepresent invention is schematically illustrated. The user device 100 isprovided with a decryptor 110 for decrypting a digital media data and adecoder 120 for decoding the decrypted digital media data and watermarkgenerator 125 for generating and embedding a watermark signal into thedecrypted and uncompressed digital media data. The user device 100 istypically assigned a user device specific indicator. In this example,that indicator is a unique machine ID 150 assigned by the manufacturer.The user device 100 may be provided with a memory unit 160 in which themachine ID 150 is stored.

In an exemplary application, the user device 100 receives an encrypteddigital media data signal 170 from a digital media data content provider300. A decryptor 110 decrypts the encrypted digital media data signal170 into a decrypted digital media data signal 175. The decrypteddigital media data signal 175 is then decoded and uncompressed by adecoder 120. A watermark generator 125 then embeds a watermark signal tothe uncompressed digital media data signal 190 from the decoder 120 toproduce a final output signal 210 which can be viewed or recorded by theuser. In another embodiment of the present invention, the decoder 120and the watermark generator 125 may be a single device that combines thetwo functions.

In order for the user device 100 to decrypt the digital media datasignal 170, the user device 100 requires a copyright license from thedigital media data provider 300. The digital media data content provider300 provides copyright license data 180 along with an encrypted digitalmedia data signal 170. The copyright license data 180 typically includesa decryption key 185 for decrypting the digital media data signal 170. Adecryptor 110 uses the decryption key 185 to decrypt the digital mediadata signal 170.

The copyright license data 180 includes digital media datacontent-related information 187. The digital media data content-relatedinformation 187 comprises information that is used to control theplayback of the digital media data content. Some examples of the digitalmedia data content-related information 187 are: the digital media datacontent subscriber/buyer (i.e. the user) information; identification ofthe digital media content provider; identification of the machine thelicense is limited to; expiration date of the license; contentdistribution rights; and geographical limitations. The digital mediadata content-related information 187 and the machine ID 150 of the userdevice 100 are processed by the watermark generator 125 to generate awatermark signal. The watermark generator 125 embeds the watermarksignal into the decoded digital media data signal 190 using any one ofthe watermarking methods generally known in the art. The resulting finaloutput signal 210 is unencrypted, uncompressed, and watermarked.

The final output signal 210 is watermarked with the watermark signalthat was derived from information in the copyright license data 180 andthe machine ID 150 of the user device 100. Such watermarking schemeenables digital media data content providers to identify the source ofany illegally distributed copies of their digital media data content.When an ill-motivated user makes illegal copies of a digital media datacontent, for example, the user's device that was used to decrypt andplay the original copy of the digital media data content will embed awatermark according to the present invention. And that watermark, havingthe user device's machine ID information as well as the digital mediadata content-related information, derived from the copyright licensedata, will allow the digital media data content provider to identify theoriginal user (e.g. the subscriber or purchaser) of the digital mediadata content and the user device 100 that was used to make the illegalcopies. Thus, even if the user device 100 is now in the possession of anunknown party, the source of the original copy of the content from whichthe unauthorized distribution began can be identified. Another benefitof the watermarking method according to the invention is that becausethe watermark is not always same for a given user device, it isgenerally less susceptible to being isolated and removed by a hacker.

In another embodiment of the present invention, the watermark signalalso may contain information on the identity of the digital media datacontent owner. The digital media data content owner would generally bethe owner of the copyright for the digital media data content.

Preferably, the type of watermark signal utilized in the watermarkingscheme according to the invention is a robust type and not fragile. Inother words, the watermark should survive further processing of thedigital media data content signal after the watermark has been embedded.For example, if the watermarked uncompressed content data from the userdevice were to be further coded and decoded or encrypted and decryptedby copyright infringers, the watermark should survive and recognizable.Methods for generating such robust watermarks are well known in the art.Some examples of such methods are disclosed in INGEMAR J. Cox ET AL.,DIGITAL WATRMARG 241-278 (Morgan Kaufmann Publishers 2002), the citedportion of which are incorporated herein by reference.

While the foregoing invention has been described with reference to theabove embodiments, various modifications and changes can be made withoutdeparting from the spirit of the invention. Accordingly, all suchmodifications and changes are considered to be within the scope of theappended claims.

1. A method of watermarking digital media data at a user devicecomprising the steps of: receiving encrypted digital media data;decrypting the digital media data into decrypted data; decoding thedecrypted data into uncompressed data; generating a watermark signalcomprising a digital media data content-related information and a userdevice specific indicator; and embedding the watermark signal into theuncompressed data.
 2. The method of claim 1, wherein the digital mediacontent-related information is derived from information contained incopyright license data corresponding to the digital media data.
 3. Themethod of claim 2, wherein the copyright license data includesinformation that is used to control playback of the digital media datacontent.
 4. The method of claim 1, wherein the user device specificindicator includes the user device's unique identification data.
 5. Themethod of claim 1, wherein the watermark signal further includesinformation on the identity of the digital media data content owner. 6.The method of claim 2, wherein the digital media data content-relatedinformation includes the digital media data content subscriberinformation.
 7. The method of claim 2, wherein the digital media datacontent-related information includes the expiration date of thecopyright license.
 8. The method of claim 2, wherein the digital mediadata content-related information includes information on distributionrights of the copyright license.
 9. The method of claim 2, wherein thedigital media data content-related information includes information onthe geographical limitations on the copyright license.
 10. The method ofclaim 1, wherein the digital media data is multimedia data.
 11. A userdevice adapted and configured to receive encrypted digital media data;decrypt the digital media data into decrypted data; decode the decrypteddata into uncompressed data; generate a watermark signal comprising adigital media data content-related information and a user devicespecific indicator; and embed the watermark signal into the uncompresseddata.
 12. The user device of claim 11, wherein the digital media data ismultimedia data.
 13. The user device of claim 11, wherein the digitalmedia data content-related information is derived from informationcontained in a copyright license data corresponding to the digital mediadata.
 14. The user device of claim 11, wherein the copyright licensedata includes information that is used to control playback of thedigital media data content.
 15. The user device of claim 13, wherein thedigital media data content-related information includes the digitalmedia data content subscriber information.
 16. A method of enforcing adigital media data content's copyright license, comprising: receiving adigital media data content at a user device; decrypting the digitalmedia data content into decrypted data in the user device; decoding thedecrypted data into uncompressed data in the user device; receiving acopyright license data in the user device; extracting at least onedigital media data content-related information from the copyrightlicense data; generating a watermark signal comprising the at least onedigital media content-related information and a user device specificindicator; embedding the watermark signal into the uncompressed data;identifying the watermark signal in a suspect copy of the digital mediadata content; and determining whether the suspect copy of the digitalmedia data content was distributed according to the copyright licensedata.
 17. The method of claim 16, wherein the digital media data ismultimedia data.
 18. The method of claim 16, wherein the digital mediadata content-related information is derived from information containedin a copyright license data corresponding to the digital media data. 19.The method of claim 16, wherein the digital media data content-relatedinformation includes digital media data content subscriber information.20. The method of claim 16, wherein the digital media datacontent-related information includes information that is used to controlplayback of the digital media data content.
 21. The method of claim 16,wherein the user device specific indicator includes the user device'sunique identification data.
 22. The method of claim 16, wherein thedigital media data content-related information includes the expirationdate of the copyright license.
 23. The method of claim 16, wherein thedigital media data content-related information includes information onthe distribution rights of the copyright license.
 24. The method ofclaim 16, wherein the digital media data content-related informationincludes information on the geographical limitations on the copyrightlicense.